Posterior Muscle Groups Research Articles

Paw-shake response and locomotion: can one CPG generate two different rhythmic behaviors?

Rhythmic limb movements like locomotion or paw-shake response are controlled by network of spinal circuits, known as central pattern generators (CPGs), as evidenced from locomotor-like and paw-shake like activity in limb peripheral nerves elicited in decerebrate or spinal animals with blocked neuromuscular transmission [4]. Unlike fictive locomotion and scratch, that are likely controlled by distinct CPGs [3], fictive paw-shake response has not been systematically investigated and it is not known whether it is controlled by a specialized CPG or by the CPG that also controls locomotion. In-vivo recordings of paw-shake motor patterns elicited by stimulation of paw skin afferents [7] have revealed high frequency hindlimb oscillations (~10 Hz) with atypical muscle synergies – reciprocal activation of anterior and posterior hindlimb muscles in each half of the paw-shake cycle; both anterior and posterior muscle groups include flexor and extensor muscles. We asked whether a paw-shake response with the atypical muscle synergies can be generated by a typical half-center locomotor CPG reciprocally activating flexor and extensor muscles. Using software AnimatLab [2] we developed a 5-segment cat hindlimb model with 12 Hill-type muscle actuators controlled by (1) a half-center CPG activating flexor and extensor muscles (two-joint muscles received both flexion- and extension-related signals [5,6]) and (2) proprioceptive input originated from the muscle spindle and Golgi tendon organ afferents. The CPG was modeled by two single-compartment spiking neurons in a half-center configuration. Other neurons (Ia-afferents, alpha-motor neurons, Ia-interneurons, and interneurons mediating autogenic and heterogenic reflex pathways) were modeled as non-spiking neurons (firing rate model based on work by [1]). Model parameters were adjusted such that computer simulations reproduced the recorded paw-shake mechanics and the anterior-posterior muscle activation patterns. The obtained results demonstrated that a half-center locomotor CPG can produce movement mechanics and muscle activity patterns typical for paw-shake responses if (1) the locomotor CPG is capable to operate at frequencies 3 to10 times higher than during locomotion and (2) synaptic weights in spinal circuits can be modified during paw-shake response. We speculate that the two conditions can be realized by sensory input from paw skin afferents.

Bone Loss after Temporarily Induced Muscle Paralysis by Botox Is Not Fully Recovered After 12 Weeks

To study the effect of unloading followed by reloading on hindlimb bone mineral content (BMC), we used botulinum toxin A (Botox). We studied the timing and degree of recovery upon restoration of muscle function. We also tested to see if reaction to Botox injection occurred as a function of the degree of expression of connexin43 (Cx43). Sixteen mice were divided by gender and genotype; wild-type equivalent (Gja1(+/flox)) and heterozygous (Gja1(+/-)) mice were injected with a single dose of 2U/100 g Botox i.m. in the quadriceps, hamstrings, and posterior calf muscle groups (day 0). Regional BMC was monitored for 12 weeks in the injected and contralateral control limb. Significant bone loss was observed in the injected limb by week 2 in the Gja1(+/flox) mice, and by week 3-4 in the Gja1(+/-) mice. By week 12, BMC in the Botox-treated limb of both male and female wild-type and heterozygous mice was still at least 14% less than that of the noninjected limb. Cortical thickness and BV/TV were lower in the Botox femur compared to the noninjected femur. The heterozygous mice tended to show a slower response to Botox injection as reflected in a slower loss of BMC. Our results show that the rapid and profound bone loss following temporary muscle paralysis is not fully recovered upon restoration of muscle function within 12 weeks. These results underscore the significance of normal muscle function in the maintenance of bone mass.

Effect of End-to-Side Repair of Proximal Nerve Stumps of Transected Peripheral Nerves on the Development of Neuroma (Experimental Study)

Neuroma is a psychologically and physically disabling problematic condition without any current standard therapy. For that reason, we investigated whether end-to-side anastomosis of the proximal end of the transected nerve into the adjacent nerve will prevent the development of neuroma in different types of nerve injuries. In this study, hind legs of 18 Sprague-Dawley female rats were used. Six groups were formed. In group I, peroneal nerves were transected and its proximal end was attached end-to-side through the epineural window to the adjacent tibial nerve. In group II, contrary to group I, an epineural window was created in the tibial nerve and the same number of sutures were employed. In group III, tibial nerve was transected proximal to the end-to-side repair site, whereas in group IV, distal segment of the nerve was cut, and an end-to-end repair procedure was repeated. In group V, unlike group I, an approximately 1-cm segment was resected and removed distal (from tibial nerve) to the end-to-side repair site. In group VI, an epineural window was created in the tibial nerve and the same number of sutures were used, and also a 1-cm distal nerve segment was resected. The rats were followed for 2 months, and then all of the groups were evaluated histopathologically, and weights of the posterior muscle groups of hind legs were evaluated. No neuroma formation was observed in the proximal stumps of peroneal nerve segments in end-to-side repair sites in groups I, III, IV, and V, and proximal stumps of the tibial nerve in group V. In group VI, neuroma formation was observed in the proximal end of the tibial nerve. When weights of the posterior muscle groups of hind legs in groups I and II were comparatively assessed, statistically significant difference was not detected. In conclusion, based on histological data obtained for proximal nerve ends and segments distal to the end-to-side repair sites, we think that end to side neurorrhaphy of the proximal end of the damaged nerve to adjacent nerve will prevent the development of neuroma without injuring the intact nerve segment.

Relationship between Soft Tissue Damages and Spinal Cord Injury in Lower Cervical Spine Trauma

Purpose: To determine the implications of soft tissue damage and to evaluate the correlations between the extent of soft tissue damages and spinal cord injury after a lower cervical spine trauma. Materials and Methods: This study analyzed the medical records, plain radiograms, and MRI of the consecutive 89 patients who underwent operative treatment in the lower cervical trauma. The radiological parameters of soft tissue damage including anterior longitudinal ligament (ALL), intervertebral disc (Disc), posterior longitudinal ligament (PLL), ligamentum flavum (LF), interspinous ligament (ISL), supraspinous ligament (SSL), posterior muscle group (PM), cord compression (CC), and cord signal changes (CS) were evaluated using plain radiograms and magnetic resonance imaging. The relationship between the level of cord injury and the type of soft tissue damage, injury type and severity was determined. Results: There was a significant correlation between the extent of cord injury and the injury type. Cord injury frequently occurred as a result of compressive extension (3 of 4 cases), combined injury (4 of 7 cases) and distractive extension (14 of 23 cases). On the other hand, only 11 of the 16 cases with compressive flexion had a cord injury. In the distractive-extension cord injury cases (2 out of 10 cases in stage I, 12 out of 13 cases in stage II) the frequency of cord injury increased with increasing degree of the soft tissue damage. The incidence of cord injury was higher in the distractive-flexion cases (stage I, 0 out of 6 cases, stage II, 8 out of 35 cases, stage III, 3 out of 5 cases), (p=0.082). Multiple logistic analysis revealed a significant correlation between the cord injury and soft tissue damage including parameters such as the injury type, PLL injury, CC and CS. There was more frequent cord injury encountered in patients with more extensive injuries to the posterior neck muscles (p=0.063). Conclusion: There was a significant correlation between the injury type and the incidence of cord injury. In distractive extension and distractive flexion, there was more increasing incidence of cord injury with increasing severity of the injury. In addition, there was a high incidence of cord injury associated with not only the injury type but also a PLL and posterior neck muscle injury.

Double Calcaneal Osteotomy

Posterior calcaneal displacement and anterior calcaneal distraction osteotomies have been recommended for surgical management of flexible flatfoot deformity. We combined these procedures for surgical management of adolescent flatfoot and late stage II posterior tibial tendon dysfunction in the adult. Lateral column distraction has been shown to reduce rearfoot valgus and forefoot abduction by stabilizing the midtarsal joint. Posterior calcaneal displacement osteotomy, which results in medial translation of the tuberosity, converts the posterior muscle group from an everter to an inverter. A supinatory moment, therefore, is created about the subtalar joint axis, which results in supination during the midstance phase of gait. These procedures may be considered when calcaneal valgus, forefoot abduction, and midtarsal joint instability are clinically significant. We also include rearfoot alignment radiographs, long leg calcaneal axial radiographs, and malleolar valgus indices to further evaluate alignment of the foot, ankle, and leg. Ideal realignment is achieved when the heel is vertical in resting calcaneal stance position, the forefoot is parallel to the rearfoot in the frontal plane, and the medial column is stabilized, with elimination of forefoot abduction.

Apport de l'IRM musculaire dans les myopathies inflammatoires

Purpose. – Inflammatory myopathies include polymyositis (PM), dermatomyositis (DM) and inclusion body myositis (IBM) which differ in terms of clinical, immuno-histological presentations, evolution and treatment. Diagnosis is based on the muscular biopsy but histological distinction between PM and IBM can be difficult; biopsies can be insufficient as well as during follow-up to detect active areas within the muscle. Current knowledge and key points. – Muscular MRI is an important tool both in the diagnosis and the follow-up of IMM in the following circumstances: • Distinction between PM and IBM: fatty infiltration and involvement of the anterior group of the thighs are characteristic of IBM whereas isolated inflammation and involvement of the three thighs or posterior muscle groups are characteristic of PM. • Biopsy guidance on the inflammatory lesions depicted on the STIR sequence either initially or after a non-conclusive biopsy. • To differentiate, active disease from steroid myopathy. Future prospects and projects. – Several multicentric trials are in development both in spectro and morphologic MRI to study hypoxic phenomenon in early course of IMM and muscular volume evaluation both in normal subjects, congenital or acquired myopathies.

Chronic Neck Pain and Cervicogenic Headaches.

Chronic axial neck pain and cervicogenic headache are common problems, and there have been significant advances in the understanding of the etiology and treatment of each. The severity and duration of pain drives the process. For patients who have had slight to moderate pain that has been present for less than 6 months and have no significant motor loss, strength training of anterior, posterior, and interscapular muscle groups coupled with body mechanics training is prescribed. After 8 weeks, if the patient is better, exercises are continued at home or in a gym. If the patient is not better, physical therapy is continued for up to 8 more weeks. In patients with motor loss or severe pain, radiographs and magnetic resonance imaging (MRI) should be ordered at the initial visit. In patients with slight to moderate pain who are not better by 4 to 6 months, plain radiographs of the neck and MRI should be ordered. Based on the results, a spinal injection is usually prescribed. If MRI reveals spinal stenosis of the central or lateral canal, or a disc herniation, an epidural corticosteroid injection should be ordered. If the epidural provides good relief, the patient can be referred for more aggressive physical therapy and repeat the epidural as needed up to a maximum of three times. If there is no pathology within the canal, medial branch blocks and intra-articular steroid injections can be ordered based on the joints that are most tender or where disc space narrowing is greatest, or MRI or radiographs are recommended. If there is excellent relief from the medial branch block and joint injections, repeat when the steroids wear off. If there is good relief again, but pain recurs, medial branch radiofrequency neurotomy is recommended. For patients with one or two level disc degeneration that has not responded, a psychologic evaluation and discography is recommended. If there are no significant psychologic abnormalities, and one or two (rarely three) painful discs, surgical consultation is recommended. Adjunctive low-dose opioid analgesics, nonsteroidal anti-inflammatory drugs, and perhaps tricyclic antidepressants are used to supplement the program at mid- and late stages.

Motor programmes for the termination of gait in humans: organisation and velocity-dependent adaptation.

1. The organisation of the muscular activities responsible for the termination of gait, their modulation as a function of the rate of progression and the associated mechanical effects were investigated in normal adults, using EMG, force plate and kinematic recordings. In particular, the braking actions in reaction to a visual cue presented at the instant of heel-strike were analysed quantitatively, with a focus on representative leg and thigh muscles of the weight-supporting (stance) and oscillating (swing) limb, during walk-and-stop trials performed at three different velocities. 2. In the stance limb, the EMG associated with braking started approximately 150 ms after the stop signal and, on average, displayed a distal-to-proximal activation sequence that primarily involved the posterior muscle groups (soleus, SOL, and hamstring, HAM). With the exception of SOL, which showed a single EMG burst, EMG patterns consisted of two or three progressively larger components occurring reciprocally in antagonistic muscles. Increasing walking speed yielded a significant reduction of the activity in distal muscles, and a simultaneous increment in proximal muscles. The mechanical effect of the earlier braking actions, estimated from the backward-directed wave of the horizontal ground reaction force, decreased in a velocity-dependent manner. 3. In the swing limb the braking activities began approximately 330 ms after the stop signal and, on average, revealed a proximal-to-distal activation sequence with the extensor groups (quadriceps, QUAD, and SOL) playing a prominent role. They always consisted of single EMG bursts, largely co-activated in the antagonist muscles. The onset latencies of the individual components showed a close correlation, and the spatio-temporal parameters were always scaled in parallel. Unlike the stance limb, the mechanical braking action associated with the final contact of the swing limb increased with walking speed. 4. The results indicate that the muscle synergies responsible for the rapid termination of gait in response to a ground-contact visual cue are produced by a relatively flexible set of motor commands modulated according to different velocity-dependent strategies in the weight-bearing limb, and by a single, fairly robust motor programme in the swing limb. Mechanical constraints related to the relative position of the centre of foot pressure and centre of body mass at the time the braking commands begin to affect external forces, may condition the difference between the two sides of the body.

Falcaustra washingtonensis n. sp. (Nematoda: Kathlaniidae) from Ambystoma tigrinum melanostictum (Caudata: Ambystomatidae) from Washington State, USA.

Falcaustra washingtonensis n. sp. (Nematoda: Kathlaniidae) from the intestine of the salamander Ambystoma tigrinum melanostictum is described and illustrated. Falcaustra washingtonensis n. sp. represents the 14th nearctic species assigned to this genus and is distinguished from other nearctic species by the distribution pattern of caudal papillae and number of posterior muscle groups of the male: 10 pairs of sessile caudal papillae--3 pairs precloacal, 1 pair adcloacal, 6 pairs postcloacal--and 5 posterior muscle groups.

Magnetic resonance imaging findings of vascular malformations of the lower extremity.

Vascular malformations are congenital lesions resulting from a defect during embryogenesis. Magnetic resonance imaging (MRI) is a very effective method for demonstrating detailed information regarding involved structures, extent, and flow characteristics of vascular malformations. In previous MRI studies, most of the emphasis is laid on the difference between high- and low-flow lesions, whereas little detailed information is available about the extent of local tissue involvement. These additional characteristics may influence the approach in treating these malformations and improve understanding of the pathogenesis. We retrospectively reviewed MRI scans of 40 patients with vascular malformations of the lower extremity. Thirty-four patients had low-flow lesions, and six had high-flow lesions. Of the low-flow lesions, 23 patients (67.6 percent) had muscle infiltration, with four of the six high-flow lesions having muscle infiltration. Nine of the 11 male patients (81.8 percent) with low-flow lesions had associated muscle infiltration, in comparison with 14 of the 23 female patients (60.9 percent) with low-flow lesions (p = 0.206). Eighty percent of the vascular malformations located on the thigh with muscle involvement had involvement of the anterior muscle group, whereas 86.6 percent of the patients with a vascular malformation located on the leg and with associated muscle involvement had at least the posterior muscle group involved (p = 0.0049). Ten patients (25 percent) of the whole group had bone infiltration. Low-flow lesions often had multifocal lesions (20.6 percent), whereas associated muscle atrophy was visible in 10 low-flow lesions and in two high-flow lesions. In low-flow lesions with muscle infiltration (n = 23), 43 percent (n = 10) had associated surrounding muscle atrophy (p = 0.009). Hypertrophy of the subcutaneous tissue was visible in 11 low-flow patients (32.4 percent). The high amount of muscle and bone involvement in vascular malformations of the lower extremity is emphasized with this study. Of particular interest was the difference in affected muscle groups. The angiosome concept is used to explain this preponderance, and we feel the angiosome concept could also be used when assessing possible intervention. The surrounding muscle atrophy and multifocal nature of these anomalies are further important considerations when assessing the possibility of intervention.

Selective expression of a ski transgene affects IIb fast muscles and skeletal structure.

The expression of a ski transgene in the bind leg muscles of mice follows a spatial and temporal pattern reminiscent of the pattern of myogenic development. Anterior muscles, which are formed earliest during development, are also the first muscles to express ski mRNA. Muscles derived from the posterior muscle group, formed later during development, exhibit delayed expression of ski mRNA. In addition, there is regional variation in ski mRNA levels within a particular muscle. Superficial regions of fast muscles, which contain a large percentage of type IIb fibers and have a high ATPase activity, express a higher level of ski mRNA than the deep portions of the same muscles. The deep regions contain a lower percentage of type IIb fibers and lower ATPase activity. The soleus, a slow muscle composed predominantly of type I fibers, expresses low ATPase activity and contains much lower levels of ski mRNA. mRNA from the ski transgene is also expressed at high levels in the osteocytes of the leg bones of 15-day and older transgenic mice. High levels of Ski protein is present in the osteocytes of the leg bones. ski expression appears to cause remodeling of the tibia and fibula. The cross-sectional area of the tibia and fibula of ski transgenic mice is significantly decreased compared to controls. X-rays of the skeletons of ski transgenic mice suggest that the bones of the entire skeleton are thinner than the bones in normal mice. Pathological stress fractures were found in several bones in the ski transgenic mice.

Distribution of muscle degeneration in Welander distal myopathy—A magnetic resonance imaging and muscle biopsy study

Seven patients with Welander distal myopathy were subjected to magnetic resonance imaging (MRI) of the lower extremity, and muscle biopsies of the tibialis anterior, soleus and vastus lateralis muscles. MRI revealed abnormalities in both the anterior and posterior compartments of the lower leg in three of the patients, and in only the posterior compartment in the rest of the patients. No MRI abnormalities were found in either the proximal muscles of the leg or in the peroneal or posterior tibial muscle groups. Affected muscles had T1- and T2-values indicating a replacement of muscle fibres with fat tissue. Muscle biopsies showed pathological changes varying from slight to severe in tibialis anterior and soleus muscles in all patients. No muscle fibre abnormalities were seen in the vastus lateralis muscle in any of the patients. In accordance with earlier reports from patients with Welander distal myopathy, there was muscle degeneration of tibialis anterior muscles corresponding to the weakness of dorsal extension of the feet, but also degeneration in the muscles of the posterior compartment. The patients did not, however, show any clinical signs of weakness related to posterior muscle groups. There is no evidence of involvement of proximal muscles of the leg clinically, with MRI or in muscle biopsies.

Coactivation of the trunk muscles during asymmetric loading of the torso.

Materials handling tasks in industry are rarely performed in the midsagittal plane. Often these tasks, labeled nonsagittally symmetric or asymmetric lifting tasks, can be expected to lead to an unequal distribution of forces between the left and right sides of the body. Because of the large number of muscles capable of resisting loads in the torso, researchers are forced to make simplifications when using biomechanical models to estimate mechanical loading of the spine during such tasks. Simplifications and assumptions regarding the coactivation of antagonistic muscles are frequently used because sufficient experimental data do not exist. The present study was designed to quantify coactivation of the trunk musculature in response to applied asymmetric loads. This load was varied in direction from an anterior midsagittal plane orientation to a posterior midsagittal plane orientation in 15-deg increments. The results showed little coactivation when the applied load directions were anterior and within 45 deg of the midsagittal orientation. When load directions were greater than 45 deg, coactivation was quantifiable in ipsilateral and posterior muscle groups.

Surgery of the Achilles Tendon and Posterior Muscle Group

Surgery of the Achilles Tendon and Posterior Muscle Group

Botulinum a toxin for the treatment of spasmodic torticollis: Dysphagia and regional toxin spread

Chemodenervation of cervical muscles with botulinum A toxin, although useful in treating spasmodic torticollis, has been associated with dysphagia. Retrospective analysis of dose and injection site (sternomastoid vs. posterior cervical muscle groups) in 26 patients (49 injections) suggested that dysphagia was related to the quantity of toxin injected into the sternomastoid muscle: dysphagia, median 150 IU (7 injections); and no dysphagia, median 100 IU (42 injections; p = 0.026 Wilcoxon test). In a prospective study (31 injections to 24 patients), limiting the dose administered to the sternomastoid to 100 IU, substantially reduced the incidence of dysphagia (0 of 31, p = 0.27, Fisher's exact test). Denervation of human orbicularis muscle fibers, 5 weeks to 4 months after injection of botulinum A toxin for the treatment of blepharospasm, was successfully demonstrated by intense, diffuse acetylcholinesterase staining. A weight-adjusted dose similar to that given for torticollis was injected into longissimus dorsi muscle in 6 albino rabbits. Using the acetylcholinesterase stain as a marker, a diffusion gradient was noted over a distance of 30 to 45 mm from the point of injection and in contralateral muscle 15 to 25 mm from this point. Thus, denervation was demonstrated to occur within a definable area which crossed anatomic barriers, such as fascia and bone. These clinical and laboratory data suggest that dysphagia following botulinum toxin therapy results from toxin spread to pharyngeal musculature from the sternocleidomastoid injection site. Limiting of the injection dose to 100 IU or less to the sternomastoid substantially decreases the incidence of this complication.

Intramuscular hemangioma. Case report and literature review

A case was presented in which a 28-year-old male presented with tenderness and stiffness in the posterior muscle group of his right leg. The patient's symptoms had been present intermittently for nearly 23 years. Recently, the pain had progressed to the point of limiting his normal daily activities. Initial conservative therapy, which consisted of Zorprin, heel lifts, and low Dye strapping, failed to alleviate the symptoms. Magnetic resonance imaging was used to identify a mass of an unknown etiology. Following orthopedic and oncologic consultation, surgical excision was advised and performed. Pathologic examination of the mass confirmed that the tumor was an intramuscular hemangioma. Classically, with intramuscular hemangiomas, patients may have soft tissue complaints, such as pain and swelling, present for years. Patients usually defer medical attention until the primary symptom of pain occurs. When a patient complains of a painful soft tissue mass of the leg, and intramuscular hemangioma should be included in the differential diagnosis. The appropriate radiographic studies and consultations should be performed, and surgical excision should be carried out.

Maximum Local Muscle Energy Metabolic Rate in Athletes

Three distance runners and three oarsmen were subjected to the prediction of maximum local energy metabolic rates of main seven muscle groups. Total energy metabolic rates and integrated bipolar surface electromyograms of the seven muscle groups were simultaneously measured during fifteen static resting and exercising items. The measurements of electromyograms were also performed during maximum voluntary contraction. Oarsmen had higher mean maximum energy metabolic rates than distance runners and non-athletes in the muscles of the anterior abdominal wall, the erector spinae muscles, the anterior femoral muscle group and the posterior crural muscle group. The muscle groups, of which mean value was higher in distance runners than in oarsmen and non-athletes, were the muscles of the buttock, the posterior femoral muscle group and the anterior crural muscle group. Nonathletes showed the least mean value in each muscle group except the posterior femoral muscle group. The present results confirmed that the maximum local muscle energy metabolic rates reflected daily prolonged heavy exercises.

Prediction of Maximum Local Muscle Energy Metabolic Rate in Voluntary Sustained Contraction

In order to determine the maximum local energy metabolic rates of seven muscle groups during maximum voluntary contraction (MVC), an application of our prediction method of local muscle energy metabolic rate (YOKOYAMA, 1980a) was considered. Total energy metabolic rates and integrated bipolar surface electromyograms of the seven muscle groups were simultaneously measured during sixteen static contraction conditions. The measurements of the electromyograms were also performed during MVC. The subjects were seven Japanese healthy males between the age of 20 and 31 years. The predicted maximum energy metabolic rates were 254.047±139. 726(mean± S.D.) [n=7] in the muscles of the anterior abdominal wall, 126.343±49.672 [n=7] in the erector spinae muscles, 131.091±35.575 [n=7] in the muscles of the buttock, 80.169±20.689 [n=7] in the posterior femoral muscle group, 154. 977±38.362 [n=7] in the anterior femoral muscle group, 75.838±38.290 [n=7] in the posterior crural muscle group and 34.475±9.583 kcal/h [n=5] in the anterior crural muscle group.

Computed tomography in dystrophia myotonica.

The calves and thighs of ten patients with dystrophia myotonica and four normal controls were studied by CT. The morphology of the anterior and posterior muscle groups of the calf and the extensor, flexor and adductor groups of the thigh were studied and their attenuation values analysed. Clinical measurement of muscle force was compared with attenuation values in each muscle group. The principal morphological change observed in diseased muscle was fatty infiltration. The amount of fatty infiltration in the calf muscles paralleled the severity of clinically apparent disease. However, in the thigh, fatty infiltration was observed in the extensors of three of the five patients who clinically had involvement of calf muscles alone. Detailed analysis of attenuation values was no better in detecting diseased muscle except of the adductor group of the thigh in those patients with both proximal and distal lower limb involvement. Comparison between muscle force and attenuation values showed a significant correlation in only the anterior muscle group of the calf in the normal controls and in those patients with clinically apparent disease of the calf muscles alone.